arrayBuffer 转base64

an ArrayBuffer new new Buffer = var (. 8); 
// Buffer stream is received back 
function _arrayBufferToBase64 (Buffer) { 
    var = binary ''; 
    var bytes = new new Uint8Array (Buffer); 
    var len = bytes.byteLength; 
    for (var I 0 =; I <len; I ++) { 
        binary + = the String.fromCharCode (bytes [I]); 
    } 
    return 'Data: file application / PDF; Base64,' + window.btoa (binary); 
} 


if picture type, splicing data: image / jpeg; base64, or data: image / png; base64,